Using rhythm theory as a heuristic device, the goals of this study are to improve measurement strategy for wandering and to evaluate effects of various pacers (level of cognitive impairment, agitation, light) upon it. Large-scale integrated activity (LSI) monitor readings are evaluated as a proxy for visual observation in estimating daily wandering. Wandering rhythm (cycle frequency, duration) and pattern (lapping, pacing, random) are compared for various levels of cognitive impairment and agitation. Finally, twilight and red light are evaluated for effects on wandering at various levels of cognitive impairment and agitation. In stage 1, a comparative descriptive design is used to obtain LSI monitor readings and to time and code wandering rhythm over a twenty-four hour period and two subsequent two hour periods for twenty-four subjects in two residential care units. Subjects are categorized by level of cognitive impairment using the Folstein Mini-Mental State Exam and the Mattis Dementia Rating Scale and rated as agitated or nonagitated using the Cohen- Mansfield Agitation Inventory. T-tests, ANOVAs, proposed to evaluate stability of LSI monitor readings and wandering rhythm variables between two hour epochs on subsequent days, the extent to which a two hour epoch represents and entire twenty four hour period, and the extent to which LSI meter readings can substitute for visually observed rhythm. Visual inspection of plots, ANOVA, regression, and contingency analyses are planned to evaluate associations of cognitive impairment and agitation to wandering rhythm and pattern. In stage 2, a multiple case study design with an embedded interrupted time series experiment using nonequivalent dependent variables is proposed to evaluate the effects of light on wandering rhythm and pattern. Controlling for level of cognitive impairment and agitation, twelve cases are studied over twenty-one two hour periods: three baseline (average ambient daylight) periods followed by three replications of three experimental periods (twilight, bright red light, and dim red light) and three no treatment periods. Visual inspection, autoregression, and t and F tests are used to evaluate the impact of various light levels upon wandering rhythm and pattern. Though wandering poses a real problem in the care of cognitively- impaired persons, weak measurement and conceptual confusion have limited studies of it. From the perspective of rhythm theory, this study aims to reduce these methodological gaps and to evaluate light as one possible intervention for wandering behavior.